This invention relates in general to hydraulic braking systems for vehicles and in particular to vehicular anti-lock braking systems not having a pump.
Anti-lock braking systems for vehicles are well known. A typical system utilizes a hydraulic control unit (HCU) incorporating several solenoid valves for control of brake fluid pressure to the wheel brakes and/or brake channels. For example, in a system utilizing an isolation valve and a dump valve for each wheel, a total of eight solenoid valves are housed in the HCU. Such a system also includes a pump housed in the HCU for dumping fluid through the dump valves and an electric motor for operating the pump.
It is desirable to reduce the cost of an anti-lock braking system by reducing the number of components required by the system, and in particular the number of components housed in the HCU. Furthermore, a reduction in the number of components housed in the HCU may result in a weight reduction of the HCU. Also, it is desirable to reduce noise emanating from the HCU during an anti-lock mode. A large source of noise is the pump and its electric motor. If the pump and motor are eliminated from an anti-lock braking system, a significant reduction in noise may be obtained.